1. The Field of the Invention
The present invention relates generally to heat management of chemical reactions and relates more specifically to a device, apparatus, and method for the purification of biogas and other sour gas streams. As used herein, the term “biogas” is to be broadly construed so as to include other sour gas streams.
2. The Relevant Technology
Heat management has many applications, including but not limited to the fuel cell industry, production of glass beads, the use of bacteria to make useful products, the production of yogurt, polymerase chain reactions, nanotechnology, and chemical reactions. For example, U.S. Pat. No. 6,881,703 discloses that a specific example of a field in which reactor temperature control is particularly important is in systems for the reforming of hydrocarbon feed streams to generate hydrogen-rich gases for the operation of hydrogen fuel cells. In a chemical reactor, regardless of its configuration or size, two variables that may affect the reaction rate are time and temperature. By controlling the heat transfer, and thus the temperature, the length of time a reaction or process requires for completion can be determined. For this reason, temperature control is a critical reactor design consideration for chemical processes. On an industrial scale, surface area-to-volume ratios may make heat transfer and temperature control difficult. Example processes wherein managing reactor heat is important include, but are not limited to, selective oxidations to make products such as ethylene oxide, phthalic anhydride, maleic anhydride, formaldehyde, acrylonitrile, acrolein, acrylic acid, methacrolein, methacrylic acid, methacrylonitrile, 1,2-dichloroethane, vinyl chloride, methanol synthesis, and Fischer-Tropsh synthesis.
Heat management is also important to purification processes. For example, many people have tried to convert biomass and other carbon-containing materials to methane or other useful products. Recent discoveries suggest that there may be an economical method to convert cellulosic and lignocellulosic materials into biogas, that is, unpure methane and/or hydrogen gas.
Biogas produced by microbial anaerobic digestion in an anaerobic digester has been used as a fuel source, usually for on-site heating or for electricity production. As a consequence of the digestion process, high concentrations of hydrogen sulfide, carbon dioxide, and water are typically observed in the biogas stream. For example, such biogas may include about 75% CH4, about 20% CO2, and significant fractions of H2S and H2O. Downstream utilization of the methane produced from the digestion process has been hindered by high concentrations of these impurities. For example, use of unpurified biogas to drive engine turbines can quickly lead to corrosion (e.g., pitting) of the turbine or other engine components.